React

React, also known as React.js or ReactJS, is an open-source JavaScript library developed by Facebook. It is a front-end or client-side library mainly used for building user interfaces (UIs) for web applications, especially when the UI status changes over time. React was created to meet the need for efficient and scalable solutions for building complex and interactive user interfaces.

React follows a component-based architecture, where user interfaces are broken down into reusable and modular components. These components can be nested within each other, promoting the reusability and maintainability of the code.

React introduces a Virtual DOM (Document Object Model), a lightweight copy of the actual DOM. When the state of a component changes, React first updates the Virtual DOM, compares it with the current state of the actual DOM, and then selectively updates only the parts that have changed. This approach enhances performance by reducing the number of direct manipulations to the DOM.

React employs a declarative syntax, making it easier to understand and debug code. Developers describe how the user interface should look based on the current state, and React ensures that the DOM is updated to match that state.

React follows a unidirectional data flow, meaning that data flows in one direction, from parent to child components. This makes it easier to understand how data changes and helps prevent unexpected side effects.

React utilizes JSX, a syntax extension for JavaScript that resembles XML or HTML. JSX allows developers to write UI components in a syntax that closely resembles the final output, making the code more readable.

Hooks, introduced in React 16.8, are functions that allow developers to use state and other React features in functional components. They provide a way to use stateful logic without the need for class components.